Internal combustion engine

ABSTRACT

A two-stroke internal combustion engine is disclosed having opposed cylinders, each cylinder having a pair of opposed pistons, with all the pistons connected to a common central crankshaft. The inboard pistons of each cylinder are connected to the crankshaft with pushrods and the outboard pistons are connected to the crankshaft with pullrods. Each opposed cylinder further comprises an integrated scavenge pump for providing positive intake pressure. This configuration results in a compact engine with a very low profile, in which the free mass forces can be substantially balanced. The engine configuration also allows for asymmetrical timing of the intake and exhaust ports through angular positioning of the journals on the crankshaft.

RELATED APPLICATION

This application claims priority from U.S. Provisional Application Ser.No. 60/482,772, filed Jun. 25, 2003, and the contents of which arehereby incorporated by reference as if recited in full herein for allpurposes.

FIELD OF THE INVENTION

The present invention relates generally to two-stroke internalcombustion engines, and more specifically to a two-stroke internalcombustion engine having a pair of opposed cylinders, each cylinderhaving a pair of opposed pistons.

BACKGROUND OF THE INVENTION

The design and production of internal combustion engines for theautomotive and light aircraft industries are well-developed fields oftechnology. To be commercially viable, any new engine configurationmust, without sacrificing performance, provide significant improvementsin the areas of energy and raw material conservation (especially theimprovement of fuel consumption), environmental protection and pollutioncontrol, passenger safety and comfort, and competitive design andproduction methods that reduce cost and weight. An improvement in one ofthese areas at the expense of any other is commercially unacceptable.

A new engine configuration must be mechanically simple so thatmechanical losses are inherently minimized, and must be well-suited tomaximizing combustion efficiencies and reducing raw emissions. Inparticular, a new engine configuration should specifically address themost significant sources of friction in internal combustion engines toreduce mechanical losses; should have combustion chambers of a volumeand design suitable for optimum combustion efficiency; and should beadaptable to utilizing advanced supercharging and fuel injectiontechniques.

A new engine configuration should be lighter in weight and preferablyhave a reduced height profile for improved installation suitability andpassenger safety. For automotive applications, a reduced height profilewould permit the engine to fit under the seat or floor area. For lightaircraft applications, a short profile would permit installation of theengine directly within the wing, without the need for an engine cowling.

A new engine configuration should be dynamically balanced so as tominimize noise and vibration. Ideally, the smallest practicalimplementation of the engine, such as a two-cylinder version, should befully balanced; larger engines could then be constructed by couplingsmaller engines together. At low-load conditions, entire portions of theengine (and their associated mechanical losses) could then be decoupledwithout unbalancing the engine.

Despite the promise of external continuous combustion technologies suchas Stirling engines or fuel cells with electric motors to eventuallyprovide low-emission high-efficiency engines for automobiles and lightaircraft, these technologies will not be viable alternatives to internalcombustion engines in the foreseeable future due to their inherentdisadvantages in weight, space, drivability, energy density and cost.The internal combustion piston engine will for many years continue to bethe principal powerplant for these applications.

The four-stroke internal combustion engine currently predominates in theautomotive market, with the four cylinder in-line configuration beingcommon. The need for at least four cylinders to achieve a suitable rateof power stroke production dictates the size and shape of this engine,and therefore also greatly limits the designers' options on how theengine is placed within the vehicle. The small cylinders of theseengines are typically not optimal for efficient combustion or thereduction of raw emissions. The four cylinder in-line configuration alsohas drawbacks with respect to passenger comfort, since there aresignificant unbalanced free-mass forces which result in high noise andvibration levels.

It has long been recognized by engine designers that two-stroke engineshave a significant potential advantage over four-stroke engines in thateach cylinder produces a power stroke during every crankshaft rotation,which should allow for an engine with half the number of cylinders whencompared to a four-stroke engine having the same rate of power strokeproduction. Fewer cylinders would result in an engine less mechanicallycomplex and less bulky. Two-stroke engines are also inherently lessmechanically complex than four-stroke engines, in that the mechanismsfor opening and closing intake and exhaust ports can be much simpler.

Two-stroke engines, however, have seen limited use because of severalperceived drawbacks. Two-stroke engines have a disadvantage in meaneffective pressure (i.e., poorer volumetric efficiency) over four-strokeengines because a significant portion of each stroke must be used forthe removal of the combustion products of the preceding power stroke(scavenging) and the replenishment of the combustion air, and istherefore lost from the power stroke. Scavenging is also inherentlyproblematic, particularly when the engine must operate over a wide rangeof speeds and load conditions. Two-stroke compression-ignition (Diesel)engines are known to have other drawbacks as well, including poorstarting characteristics and high particulate emissions.

Modem supercharging and fuel injection methods can overcome many of thelimitations previously associated with two-stroke engines, making a twocylinder two-stroke engine a viable alternative to a four cylinderfour-stroke engine. A two cylinder two-stroke engine has the sameignition frequency as a four cylinder four-stroke engine. If thetwo-stroke engine provides a mean effective pressure ⅔rds that of thefour-stroke, and the effective displacement volume of each cylinder ofthe two-stroke is increased to 3/2 that of the four-stroke, then the twoengines should produce comparable power output The fewer but largercombustion chambers of the two-stroke would be a better configurationfor improvement of combustion efficiency and reduction of raw emissions;the two-stroke could also dispense with the valves of the four-strokeengine, thus permitting greater flexibility in combustion chamberdesign.

Current production engines are also known to have significant sources offriction loss; increased engine efficiency can be achieved by reducingthese friction losses. The largest sources of friction loss in currentproduction automotive engines, accounting for approximately half of allfriction losses, are the result of the lateral forces produced by therotating connecting rods acting on the pistons, pushing them against thecylinder walls. The magnitudes of these losses are a function of thecrankshaft throw, r, divided by the connecting rod length, l; the ratiois often designated λ (lambda). Decreasing λ, either by increasing theeffective connecting rod length or decreasing the crankshaft throw,potentially yields the greatest overall reduction in friction loss.

The losses due to the contact of the pistons (or more correctly, thepiston rings) with the cylinder walls are also a function of the meanvelocity of the pistons with respect to the cylinder walls. If thepistons can be slowed down while maintaining the same power output,friction losses will be reduced.

Another significant source of friction loss in current productionengines are the large forces acting on the crankshaft main bearings. Atypical four cylinder inline engine has five crankshaft main bearings,which are necessary because there are literally tons of combustion forcepushing down on the crankshaft; these forces must be transferred to thesupporting structure of the engine. Both the crankshaft and thesupporting structure of the engine must be designed with sufficientstrength (and the corresponding weight) to accommodate these loads.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a two cylinder two-strokeinternal combustion engine having improved efficiency, a reduced heightprofile and lower weight for improved installation suitability,substantially total dynamic balance, and mechanical simplicity forreduced production costs.

Accordingly, an engine mechanism is disclosed that utilizes a singlecrankshaft and two opposed cylinders with integrated scavenging pumps.Each cylinder contains opposed inner and outer pistons reciprocablydisposed to form a combustion chamber between them. Pushrods areprovided to drivingly couple the inner pistons to the crankshaft, andpullrods to drivingly couple the outer pistons to the crankshaft.

Further in accordance with the invention, the pushrods share a commoncrankshaft journal as well as both pair of respective pullrods eachshare a common journal for receiving the driving forces from therespective pullrods and pushrods. Each cylinder has air intake ports andexhaust ports formed near its respective ends, controlled by therespective inner and outer pistons.

In accordance with embodiments of the invention, the pullrod and pushrodjournals for each cylinder are arranged asymmetrically so that theexhaust ports of the associated cylinder open before its air intakeports open, and close before its air intake ports close.

In accordance with embodiments of the invention, each inner piston onits end remote from the combustion chamber has a smooth end face that isconvexly curved in a plane perpendicular to the longitudinal axis of thecrankshaft. An associated pushrod has a concavely shaped outer endsurface that slidingly engages the curved end face of the inner piston.This pushrod configuration serves to effectively lengthen the pushrods;thereby reducing friction losses and improving dynamic balance.

In accordance with embodiments of the invention, two pullrods for eachcylinder are provided for receiving the driving force from the outerpistons. The two pullrods are on opposite sides of the cylinder, withtheir inner ends encircling an associated journal of the crankshaft,while their ends remote from the crankshaft are coupled to a bridge thatis pivotally coupled to the remote end of the respectively associatedouter piston.

Maximum power efficiency from an engine according to the presentinvention is best achieved by applying pressurized air to the intakeports of each cylinder. In accordance with embodiments of the invention,an engine with asymmetric timing includes two scavenging pumps, each ofwhich are integrated in the respective left and right cylinders anddriven by respective outer pistons, are coupled to intake ports of anassociated cylinder to apply pressurized intake fluid to the intakeports of that associated cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further described in connection with the accompanyingdrawings, in which:

FIG. 1 is a partial cutaway isometric view of an engine in accordancewith an embodiment of the present invention;

FIGS. 2 and 3 are top cross-sectional views of the left cylinder in thetop dead center and bottom dead center positions, respectively, inaccordance with an embodiment of the present invention;

FIG. 4 is a cross-sectional side view of the left cylinder, inaccordance with an embodiment of the present invention;

FIG. 5 is a side cross-sectional view of a left cylinder liner thatdefines in-part the left combustion chamber, in accordance with anembodiment of the present invention;

FIG. 6A is a cross-sectional view along the cut line 6A-6A of FIG. 5;

FIG. 6B is a cross-sectional view along the cut line 6B-6B of FIG. 5;

FIGS. 7A is a side and cross-sectional view of a left cylinder linerthat defines in-part the left combustion chamber and at least one row ofcombination-intake ports at an intake end, in accordance with anembodiment of the present invention;

FIG. 7B is a cross-sectional view along the cut line 7B-7B of FIG. 7A;

FIG. 8A is a graph representing symmetric timing of the opening andclosing of the intake ports and the exhaust ports as a function ofcrankshaft angle;

FIG. 8B is a graph representing asymmetric tiling of the opening andclosing of the intake ports and the exhaust ports as a function ofcrankshaft angle in accordance with the present invention;

FIG. 9 is a side cross-sectional view of an engine with the crankshaftat an angle of rotation of 270°, in accordance with an embodiment of thepresent invention;

FIG. 10 is a graph representing asymmetric timing of the opening andclosing of the intake ports and the exhaust ports as a function ofcrankshaft angle in accordance with the present invention;

FIG. 11 is a side cross-sectional view of an engine with a slidingcylinder linear in accordance with an embodiment of the presentinvention;

FIG. 12 is a side cross-sectional view of the left cylinder including aleft face and left inner piston combustion face near top dead centerforming a torroidal combustion chamber, in accordance with an embodimentof the present invention;

FIGS. 13A and 13B are partial cross-sectional views of an engineincluding the left cylinder comprising an intermittent-contact sparkignition system in a disengaged and engaged position, respectively, inaccordance with an embodiment of the present invention;

FIG. 14 is a partial cross-sectional view of the left cylindercomprising a sliding-contact ignition system, in accordance with anembodiment of the present invention;

FIG. 15A is a partial side cross-sectional view of a left outer pistonhead wherein the glow plug extends into a spherical cavity formed in theleft outer piston head extending from the left inner piston combustionface, in accordance with an embodiment of the present invention;

FIG. 15B is a partial side cross-sectional view of a left outer pistonhead wherein the glow plug extends into a swirl cavity formed in theleft outer piston head extending from the left inner piston combustionface, in accordance with an embodiment of the present invention;

FIG. 15C is a partial side cross-sectional view of a left outer pistonhead wherein the glow plug extends into a cavity bottom of an elongatedcavity formed in the left outer piston head extending from the leftinner piston combustion face, in accordance with an embodiment of thepresent invention;

FIG. 16 is a top exploded cross-sectional view of the crankshaft,left/right pullrods and left/right pushrods, in accordance with anembodiment of the present invention;

FIG. 17 is an assembled top view of the embodiment of FIG. 16;

FIG. 18 is an isometric exploded view of the left/right pushrods, thesecond and third crankshaft components, and the second roller bearing,in accordance with an embodiment of the present invention;

FIG. 19 is an isometric assembled view of a crankshaft, in accordancewith an embodiment of the present invention;

FIG. 20 is a cross-sectional isometric assembled view of the crankshaftof FIG. 19, in accordance with an embodiment of the present invention;

FIG. 21 is a partial cutaway isometric view of an engine, in accordancewith an embodiment of the present invention;

FIG. 22 is a partial cut-away view of a balancing system comprising abalancing system housing, a counter weight, and a planetary gearassembly, in accordance with an embodiment of the present invention;

FIG. 23 is a cross sectional view along the cut line 23-23 of FIG. 3showing the left bridge comprising a bridge concave surface that isadapted to be slidingly received in convex pull surface of the rightouter piston in accordance with an embodiment of the present invention;

FIG. 24 is a schematic top view of an engine comprising a plurality ofOPOC engines, coupled to a common crankshaft in side-by-side parallelrelationship, in accordance with an embodiment of the present invention;

FIG. 25 is a schematic front view of an engine comprising a plurality ofan odd number of OPOC engine cylinders coupled to a common crankshaft inan equally-spaced radial relationship, in accordance with an embodimentof the present invention; and

FIG. 26 is a schematic front view of an engine comprising a plurality ofOPOC engines coupled to a common crankshaft in an equally-spaced radialrelationship, in accordance with an embodiment of the present invention.

DESCRIPTION OF THE INVENTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof wherein like numeralsdesignate like parts throughout, and in which is shown by way ofillustration specific embodiments in which the invention may bepracticed. It is to be understood that other embodiments may be utilizedand structural or logical changes may be made without departing from thescope of the present invention. Therefore, the following detaileddescription is not to be taken in a limiting sense, and the scope of thepresent invention is defined by the appended claims and theirequivalents.

FIG. 1 is a partial cutaway isometric view of an engine 10 in accordancewith an embodiment of the present invention. The engine 10 comprises ahousing 103 containing a left cylinder 100, an axially aligned rightcylinder 200 opposite the left cylinder 100, and a crankshaft 300located there between. FIG. 1 depicts the engine 10 at a crankshaftangle of 0° or top dead center (TDC).

FIGS. 2 and 3 are top cross-sectional views of the left cylinder 100 inthe DC and bottom dead center (BDC) positions, respectively, inaccordance with an embodiment of the present invention. As shown inFIGS. 1, 2 and 3, the left cylinder 100 comprises a left cylinder liner130, a left outer piston 110 and a left inner piston 120. The leftcylinder liner 130 comprises a left cylinder liner outer surface 132 anda bore defining a left cylinder liner bore surface 139. The leftcylinder liner 130 further comprises a left cylinder liner intake end136 and a left cylinder liner exhaust end 138. The left cylinder linerintake end 136 comprises a plurality of left intake ports 161 and theleft cylinder liner exhaust end 138 comprises a plurality of leftexhaust ports 163, which will be further described below.

The left outer piston 110 comprises a left outer piston head 116 and aleft outer piston plunger 118 opposite the left outer piston head 116.The left outer piston head 116 terminates at a left outer pistoncombustion face 111. The left outer piston head 116 is adapted to beslidingly received in close fitting engagement with the left cylinderliner bore surface 139 at the left cylinder liner intake end 136.

The left inner piston 120 comprises a left inner piston head 126 and aleft inner piston push end 124 opposite the left inner piston head 126.The left inner piston head 126 terminates at a left inner pistoncombustion face 121. The left inner piston head 126 is adapted to beslidingly received in close fitting engagement with the left cylinderliner bore surface 139 at the left cylinder liner exhaust end 138.

The left outer piston 110, the left inner piston 120, and the leftcylinder liner 130 define a left combustion chamber 150.

Similarly, as shown in FIG. 1, the right cylinder 200 comprises a rightcylinder liner 230, a right outer piston 210 and a right inner piston220. The right cylinder liner 230 comprises a right cylinder liner outersurface 232 and a bore defining a right cylinder liner bore surface 239.The right cylinder liner 230 further comprises a right cylinder linerintake end 236 and a right cylinder liner exhaust end 238. The rightcylinder liner intake end 236 comprises a plurality of right intakeports 261 and the right cylinder liner exhaust end 238 comprises aplurality of right exhaust ports 263, which will be further describedbelow.

The right outer piston 210 comprises a right outer piston head 216 and aright outer piston plunger 218 opposite the right outer piston head 216.The right outer piston head 216 terminates at a right outer pistoncombustion face 211. The right outer piston head 216 is adapted to beslidingly received in close fitting engagement with the right cylinderliner bore surface 239 at the right cylinder liner intake end 236.

The right inner piston 220 comprises a right inner piston head 226 and aright inner piston push end 224 opposite the right inner piston head226. The right inner piston head 226 terminates at a right inner pistoncombustion face 221. The right inner piston head 226 is adapted to beslidingly received in close fitting engagement with the right cylinderliner bore surface 239 at the right cylinder liner exhaust end 238.

The right outer piston 210, the right inner piston 220, and the rightcylinder liner 230 define a right combustion chamber 250.

The left outer piston 110 and the right outer piston 210 are coupled toa pair of common journals, outer piston journals 311, on the crankshaft300. The left outer piston 110 is coupled to the crankshaft 300 by meansof a pair of left pullrods 411, one on either side of the left cylinderliner 100. Similarly, the right outer piston 210 of the right cylinder200 is coupled to the crankshaft 300 by two right pullrods 421. Sincethe pullrods 411, 421 are typically always in tension during normalengine operation and need only support a minor compressive force duringengine startup, as will be further explained below, they may berelatively thin and therefore lightweight. The long length of thepullrods 411, 421 relative to the crankshaft throws serves to reducefriction losses in the engine 10. The pullrods 411, 421 and how theycouple with the crankshaft 300 will be further described below.

The left and right pullrods 411, 421 are coupled to the left and rightouter pistons 110, 210 by means of left and right bridges 170, 270. Theleft and right bridges 170, 270 comprise a bridge concave surface 173that is adapted to be slidingly received in convex pull surface 172 ofthe left outer piston 110, which will be further described below.

The left inner piston 120 and the right inner piston 220 are coupled toa common journal, an inner piston journal 312, on the crankshaft 300.During normal engine operation, the left/right pushrods 412, 422 arealways under compression. The left inner piston 120 of the left cylinder100 is coupled to the crankshaft 300 by means of a left pushrod 412; theright inner piston 220 of the right cylinder 200 is similarly coupled tothe crankshaft 300 by a right pushrod 422. The left/right pushrods 412,422 have left/right concave ends 413, 423 that ride on left/right convexsurfaces 125, 225 on the left/right inner piston push ends 124, 224 ofthe left/right inner pistons 120, 220, respectively. This arrangementserves to effectively lengthen the pushrod length, which reducesfriction losses and helps dynamically balance the engine 10. Theleft/right pushrods 412, 422 and the left/right convex surfaces 125, 225will be further described below.

The four pistons 110, 120, 210, and 220 have a plurality of piston rings112, 122, 212, and 222, respectively, located both behind the combustionfaces 111, 121, 211, 221 and further along the piston heads 116, 118,216, 218 to prevent the escape of fluid from between the piston heads116, 118, 216, 218 and the bore surface 115, 215. Additional pistonrings may be employed.

As stated above, the left/right cylinder liners 130, 230 each have aplurality of left/right intake ports 161, 261 and left/right exhaustports 163, 263. On the left cylinder 100, by way of example, the leftouter piston 110 opens and closes the left intake ports 161 and the leftinner piston 120 opens and closes the left exhaust ports 163. The timingof the opening and closing of the left/right intake ports 161, 261 andleft/right exhaust ports 163, 263 will be described below.

The housing 103 is adapted to house the left cylinder 100, the rightcylinder 200, and the crankshaft 300. The housing 103 comprises a leftcylinder cavity 104, a right cylinder cavity 204, and a crankshaftcavity 304, adapted to house the left cylinder 100, the right cylinder200, and the crankshaft 300, respectively. The left cylinder cavity 104defines a left plunger sliding surface 106 and terminates with a lefthousing end cap 107. The left plunger 118 is adapted to be slidinglyreceived in close fitting sealed engagement with the left plungersliding surface 106. The left plunger 118, the left housing end cap 107,and the left plunger sliding surface 106 define a first left scavengingchamber 105.

The left cylinder cavity 104 is divided into two volumes by a pair ofleft sleeve seals 123: one defining in-part the crankshaft cavity 304and the other defining a second left scavenging chamber 109. The leftsleeve seals 123 are tubular members each having an inner bore diameteradapted so that one of the left pullrods 411 can pass therethrough.

FIG. 4 is a cross-sectional side view of the left cylinder 100, inaccordance with an embodiment of the present invention. The left sleeveseals 123 comprise a suitable cross-sectional shape, such as circular orelliptical, so as to accommodate the range of motion of the leftpullrods 411 during operation of the engine 10. As shown, the leftpullrods 411 are in a lowered position wherein the crankshaft (notshown) is in the BDC position.

Referring again to FIGS. 1-3, a sleeve end 169 of the left sleeve seal123 is coupled to the left plunger 118 such that the left sleeve seal123 is carried by the left plunger 118 as the left plunger 118translates axially during engine operation.

The left cylinder cavity 104, the left plunger 118, the left cylinderliner 130, and the left sleeve seals 123 define the second leftscavenging chamber 109. The second left scavenging chamber 109 and thecrankshaft cavity 304 are sealed from fluid communication by theengagement of each of the left sleeve seals 123 with left sleeve sealrings 128 coupled to the housing 103. The left sleeve seal rings 128 areadapted to allow the translation of the left sleeve seals 123 thereinwhile preventing fluid communication between the second left scavengingchamber 109 and the crankshaft cavity 304.

In one embodiment in accordance with the present invention, intake fluidis communicated through the second left scavenging chamber 109 andlubricating and/or cooling fluid is communicated through the crankshaftcavity 304.

The first left scavenging chamber 105 is in fluid communication with thesecond left scavenging chamber 109 by at least one first scavengingchamber port 165, a left scavenging conduit 166, and a second scavengingchamber port 167. The first scavenging chamber port 165 provides fluidcommunication between the first left scavenging chamber 105 and the leftscavenging conduit 166, and the second scavenging chamber port 167provides fluid communication between the left scavenging conduit 166 andthe second left scavenging chamber 109.

Similarly, the right cylinder cavity 204 defines a right plunger slidingsurface 206 and terminates with a right housing end cap 207. The rightplunger 207 is adapted to be slidingly received in close fittingengagement with the right plunger sliding surface 206. The right plunger207, the right housing end cap 207, and the right plunger slidingsurface 206 define a first right scavenging chamber 205.

In substantially similar arrangement as the left cylinder 100, the rightcylinder cavity 204 is divided into two volumes by a pair of rightsleeve seals 223: one defining in part the crankshaft cavity 304 and theother defining a second right scavenging chamber 209.

Scavenging Pump

The mechanical components that make up the first and second scavengingchambers 105, 205, 109, 209 are herein referred to as a scavenging pump.Scavenging pump operation will be described by way of example. Assumethat the left cylinder 100 is undergoing a power stroke wherein thecrankshaft 300 is at 90° past “top dead center” (TDC), such as shown inFIG. 2. During the power stroke, the left outer piston 110 and the leftinner piston 210 are driven apart by the high pressure fluid within theleft combustion chamber 150 produced during combustion. The left outerpiston 110 and therefore the left outer piston plunger 118 is driventowards the left housing end cap 107, which in turn decreases thevolume, and increases the pressure within the first left scavengingchamber 105, as shown in FIG. 3.

At a predetermined pressure; a one-way valve 168 adjacent the firstscavenging chamber port 165, among other suitable locations, releaseshigh-pressure fluid from the first left scavenging chamber 105 throughthe left scavenging conduit 166 and into the second left scavengingchamber 109. At a predetermined time during the high-pressure fluidrelease from the first left scavenging chamber 105, the left intakeports 161 are opened to permit the high pressure fluid in the secondleft scavenging chamber 109 to enter the left combustion chamber 150.

The intake fluid in the second left scavenging chamber 109 is furthercompressed by the movement of the left outer pistons 110. In accordancewith an embodiment of the present invention, the left exhaust ports 163are closed before the left intake ports 161, wherein the pressure of theintake fluid further increases as the left outer piston 110 moves distalto the crankshaft 300.

During the compression stroke, the left outer piston 110 and the leftinner piston 210 are driven together by the left pullrods 411 and theleft pushrods 412, respectively. The left outer piston 110 and thereforethe left outer piston plunger 118 is driven away from the left housingend cap 107, which in turn increases the volume, and decreases thepressure within the first left scavenging chamber 105. This closes theone-way valve 168 adjacent the first scavenging chamber port 165 andopens one or more one-way intake valves 182 in the left housing end cap107, drawing in intake fluid there through.

Intake Ports

FIG. 5 is a side cross-sectional view of a left cylinder liner 130 thatdefines in-part the left combustion chamber 150, in accordance with anembodiment of the present invention. The left cylinder liner 130comprises a left cylinder liner intake end 136 comprising at least onerow of first intake ports 161 and at least one row of second intakeports 162. The left cylinder liner 130 further comprises a left cylinderliner exhaust end 138 comprising at least one row of exhaust ports 163.

FIGS. 6A and 6B are cross-sectional views of the first and second intakeports 161, 162 respectively, in accordance with an embodiment of thepresent invention. Each of the first intake ports 161 comprise a radialflow channel 164 that is adapted to direct intake fluid into the leftcombustion chamber 150 in a radial direction with respect to the leftcylinder liner axis X-X and at a retrograde angle alpha in a directionaway from the exhaust end 138 and towards the intake controlling leftouter piston 110, as shown in FIG. 3. The radial flow channels 164 areadapted to direct intake fluid into the central region of the leftcombustion chamber 150 and away from the left cylinder liner boresurface 139. Determination of a suitable retrograde angle alpha isdependent on the pressure of the intake fluid supplied to the firstintake ports 161, the pressure within the left combustion chamber 150,intake fluid temperature, intake fluid velocity, intake fluidcomposition, among others. A central intake-fluid zone flow pattern isestablished by the first intake ports 161 characterized by asubstantially-non-swirling fluid path.

Each of the second intake ports 162 comprise a tangential flow channel364 that is adapted to direct intake fluid in a substantially tangentialdirection with respect to the left cylinder liner bore surface 139 andat a retrograde angle beta in a direction away from the exhaust end 138and towards the intake controlling left outer piston 110, as shown inFIG. 3. The tangential flow channels 364 are adapted to direct intakefluid substantially along the left cylinder liner bore surface 139. Thetangential flow channels 364 are adapted to establish a sideintake-fluid zone adjacent the central intake-fluid zone and the leftcylinder liner bore surface 139. Determination of a suitable retrogradeangle beta is dependent on the pressure of the intake fluid supplyingthe second intake ports 163, pressure in the left combustion chamber150, intake fluid temperature, intake fluid composition, among others.The flow pattern established by the second intake ports 163 ischaracterized by a substantially-swirling fluid path in the combustionchamber 150.

In operation of the OPOC engine 10, as the left outer piston 110translates in a retrograde direction (away from the crank shaft), thesecond intake ports 162 open. The second intake ports 162 establish aback flow of the exhaust (combustion) fluid about the second intakeports 162 and later a swirl intake-fluid flow pattern that displaces theexhaust fluid that lies adjacent the left cylinder liner bore surface139 because the centrifugal forces are pushing the heavier cold intakefluid away from the axis X-X. As the left outer piston 110 translatesfurther in a retrograde direction, the first intake ports 161 are openednow in combination with the second intake ports 162. The first intakeports 161 establish a central flow pattern that displaces the exhaustfluid that is found in the central region of the left combustion chamber150. This central flow is at the beginning not disturbed by the flowthrough the second intake ports 162 due to the back flow when the secondintake ports 162 open.

The combination of the central intake-fluid zone flow pattern and theside intake-fluid zone adjacent the central intake-fluid zone and theleft cylinder liner bore surface 139 provides a relatively flat slug orfluid front 177 between the intake fluid 175 and the exhaust fluid 176.When the fluid front 177 reaches the exhaust ports 163, the intake fluid175 has substantially scavenged or displaced the exhaust fluid 176 fromthe left cylinder liner 130. 5 FIGS. 7A and 7B are a side andcross-sectional view of a left cylinder liner 130 that defines in-partthe left combustion chamber 150 and at least one row ofcombination-intake ports 461 at an intake end 136, in accordance with anembodiment of the present invention. Each of the combination intakeports 461 comprise a combination flow channel 464 comprising a radialsurface 561 and a generally tangential surface 661 that is adapted todirect intake fluid into the left combustion chamber 150 in both aradial and tangential direction with respect to the left cylinder lineraxis X-X and at a retrograde angle gamma in a direction away from theexhaust end 138 and towards the intake controlling left outer piston110, as shown in FIG. 3.

This combination intake port 461 is particularly advantageous in smallengines where there is insufficient space to put in multiple rows ofintake ports. A single row that has integrated both functions: directingthe flow toward the center of the left combustion chamber 150 whileproviding the necessary swirl is provided.

FIG. 7A approximately illustrates the resulting flow pattern 117 in theleft combustion chamber 150. In effect, a well formed front, or slug, ofintake fluid 175 extends substantially the width of the left combustionchamber 150 and effectively displaces the exhaust fluid 176 from thecombustion chamber 150 towards the exhaust ports 163. The combination ofintake port geometry (height, width, length, radial, tangential, amongothers), inner and outer piston timing, intake fluid pressure andtemperature, among others, provides that substantially all of theexhaust fluid 176 is displaced from the combustion chamber 150 duringthe exhaust phase. Also, the above parameters provide that substantiallyno potentially fuel-rich intake fluid 175 is permitted to escape theexhaust ports 163.

The mentioned flow pattern developed in the combustion chamber 150provides increase in engine performance and a greatly reduced emissionof fuel-rich pollutants.

FIG. 8A is a graph representing symmetric timing of the opening andclosing of the intake ports and the exhaust ports as a function ofcrankshaft angle. An intake port curve 22 a shows the opening andclosing of the intake ports as a symmetric curve about the axis m. Anexhaust port curve 20 a shows the opening and closing of the exhaustports as a symmetric curve about the axis m and about the intake portcurve 22 a. The exhaust port curve 20 a shows that the exhaust portsopen before the intake ports open, and the exhaust ports close after theintake ports close. This timing configuration is not ideal, as therewill be a pressure loss out of the last-closing exhaust ports.

FIG. 8B is a graph representing asymmetric timing of the opening andclosing of the intake ports and the exhaust ports as a function ofcrankshaft angle, in accordance with an embodiment of the presentinvention. An intake port curve 22 b shows the opening and closing ofthe intake ports as a symmetric curve offset from the axis m. An exhaustport curve 20 b shows the opening and closing of the exhaust ports as asymmetric curve about the axis m. The exhaust port curve 20 b shows thatthe exhaust ports open before the intake ports open, and the exhaustports close before the intake ports close. This timing configuration issuitable for maintaining or increasing pressure within the combustionchamber after the exhaust ports close with no loss out of thefirst-to-close exhaust ports.

One relationship of pistons and connecting rods, with associated timingsequences, is described in further detail in U.S. Pat. No. 6,170,443 andPCT/US 03/08708 entitled ENGINE WITH POWER GENERATING CAPABILITY, whichis under common ownership with this application, and is incorporatedherein by reference in its entirety for all purposes.

Other timing sequences are appreciated. In one embodiment, asymmetrictiming may be desired to reduce the complexity of the system. Varioustiming sequences in accordance with embodiments of the present inventionare described herein.

Referring again to FIG. 1, the outer piston journals 311 and the innerpiston journal 312 are uniquely positioned with respect to thecrankshaft rotational axis 310. The inner piston journal 312 is furtherfrom the crankshaft rotational axis than the outer piston journals 311,resulting in greater travel for the left/right inner pistons 120, 220than for the left/right outer pistons 110, 210. Further, the innerpiston journal 312, which directly controls the translation of theleft/right inner pistons 120, 220 which open and close the left/rightexhaust ports 163, 263 in the left/right cylinders 100, 200, areangularly advanced, while the outer piston journals 311 which directlycontrol the translation of the left/right outer pistons 110, 210, whichopen and close the intake ports, such as the first and second intakeports 161, 162, are angularly retarded.

The above configuration provides an asymmetric timing that has theexhaust ports 161 opening before the intake ports 161, 162 and theexhaust ports 161 closing before the intake ports 161, 162 close. Thisarrangement provides that no intake fluid is permitted to exhaustthrough the exhaust ports 162, and for substantially complete scavengingof the combustion chamber 150.

Referring again to FIGS. 2 and 3, the left outer piston 110 selectivelyopens and closes the intake ports 261, 262, 461 to facilitate desiredtiming of the intake fluid into the left combustion chamber 150. Anembodiment in accordance with the present invention comprises asymmetrictiming wherein at the end of the firing or power stroke, before bottomdead center (BBDC) exhaust ports 163 open at approximately 75 degrees,measured as the amount of crankshaft rotation. And, the second intakeports 162 open at approximately 45 degrees. Conversely, at the beginningof the compression stroke, after bottom dead center (ABDC), the exhaustports 163 close at approximately 45 degrees, and the second intake ports162 close at approximately 55 degrees, for example.

Variable Port Timing

FIG. 9 is a side cross-sectional view of an engine 12 with thecrankshaft 1300 at an angle of rotation of 270°, in accordance with anembodiment of the present invention. At this angle, the left outer andinner pistons 1110, 1120 of the left cylinder 1100 are converged, withthe left intake and left exhaust ports 1161, 1163 being closed. Theintake fluid between the left outer and inner pistons 1110, 1120, iscompressed there between.

The right cylinder 1200 is completing its power stroke, with the rightouter and inner pistons 1210, 1220 having moved apart with the rightintake and exhaust ports 1261, 1263 open.

The amount of time that the intake and exhaust ports 1161, 1261, 1163,1263 are open to bring in intake (pre-combustion) fluid and blow outexhaust fluid, respectively, is determined by a number of fixed andvariable factors. The fixed factors are, among others, the stroke lengthof the outer and inner pistons 1110, 1210, 1120, 1220 and the distancebetween the intake and exhaust ports 1161, 1261, 1163, 1263. Thevariable factors include, among other things, the engine speed andintake fluid pressure.

The opening and closing of the intake and exhaust ports 1161, 1261,1163, 1263 is preferentially timed so as to allow a substantiallycomplete blowout of exhaust fluid from the respective left/rightcombustion chamber 1150, 1250 by the incoming intake fluid, but not solong so as to allow intake fluid to exit the exhaust ports 1163, 1263.Insufficient blowout of exhaust fluid will reduce engine 12 performance.Escape of intake fluid out of the exhaust ports 1163, 1263 contributesto airborne pollution.

The time in which the intake and exhaust ports 1161, 1261, 1163, 1263are open is directly related to engine speed, all else being constant.The intake and exhaust ports 1161, 1261, 1163, 1263 are open for ashorter period of time for a higher engine speed than that for a slowerengine speed. For a constant intake fluid pressure, the amount of intakeand exhaust fluid displacement is therefore directly related to enginespeed. An ideal complete displacement of exhaust fluid by intake fluidis achievable for only one engine speed.

Sliding Cylinder Liner

In an embodiment in accordance with the present invention, variable porttiming is provided to adjust the time in which the intake and exhaustports 1161, 1261, 1163, 1263 are open relative to engine speed.Referring again to FIG. 9, the housing 1103 comprises a left cylindercavity 1104, a right cylinder cavity 1204, and a crankshaft cavity 1304,adapted to house the left cylinder 1100, the right cylinder 1200, andthe crankshaft 1300, respectively. The left cylinder cavity 1104 definesa left cylinder liner bore 1134 adapted to slidingly receive in closefitting engagement with the left cylinder liner 1130. Suitable slidingseals (not shown) are provided between the left cylinder liner bore 1134and the left cylinder liner 1130.

The axial location of the left cylinder liner 1130 relative to the leftcylinder liner bore 1134 is preferentially controlled. During slowengine speed operation, the left cylinder liner 1130 is translatedaxially towards the crankshaft 1300. The movement of the left cylinderliner 1130 towards the crankshaft 1300 effectively shortens the time inwhich the left exhaust ports 1163 are open. In an extreme example, theleft cylinder liner 1130 moves an axial distance towards the crankshaft1300 sufficient so that the left inner piston 1120 only partially opensthe left exhaust ports 1163 further reducing the time in which theexhaust fluid exits the left exhaust ports 1163.

Similarly, the axial location of the right cylinder liner 1230 relativeto the right cylinder liner bore 1234 is preferentially controlled.During slow engine speed operation, the right cylinder liner 1230 istranslated axially towards the crankshaft 1300. The movement of theright cylinder liner 1130 towards the crankshaft 1300 effectivelyshortens the time in which the right exhaust ports 1163 are open. In anextreme example, the right cylinder liner 1130 moves an axial distancetowards the crankshaft 1300 sufficient so that the right inner piston1120 only partially opens the right exhaust ports 1263 further reducingthe time in which the exhaust fluid exists the right exhaust ports 1263.

FIG. 10 is a graph representing asymmetric timing of the opening andclosing of the intake ports and the exhaust ports as a function ofcrankshaft angle, in accordance with an embodiment of the presentinvention. A first intake port curve 22 b shows the opening and closingof the intake ports as a symmetric curve offset from the axis of a firstexhaust port curve 20 b which shows the opening and closing of theexhaust ports. Movement of the left cylinder liner 1130 provides ashifting of the timing of the intake and exhaust ports, an example shownas a second intake port curve 22 c and second exhaust port curve 20 c.By moving the left cylinder liner 1130, preferential port timing inrelation to the engine speed and load is achievable.

The cylinder liner 1130, 1230 is moved in an axial direction by a numberof suitable means. In one embodiment in accordance with the presentinvention, the cylinder liner 1130, 1230 is moved using an actuatingmeans, including, but not limited to, an electric motor, hydraulicactuator, and the like. The actuating means is controlled by a feedbackcontrol system (not shown) that controls the position of the cylinderliner 1130, 1230 to a predetermined position in accordance withpredetermined engine speed, or other performance parameter.

In another embodiment in accordance with the present invention, fluidpressure acting upon a portion of the cylinder liner overcoming arestoring element is used to position the cylinder liner 1130, 1230.FIG. 11 is a side cross-sectional view of an engine 12 in accordancewith an embodiment of the present invention. Looking at the rightcylinder 1200, the left cylinder 1100 being similarly arranged (notshown), the housing 1103 comprises a fluid inlet 1264 adapted to providecontrollable hydraulic pressure on the exhaust end 1238 of the rightcylinder liner 1230. The right cylinder liner 1230 further comprises oneor more flanges 1237 suitable for coupling with a bias member 1259. Thebias member 1259 is adapted to provide a restoring force on the rightcylinder liner 1230 as the right cylinder liner 1230 is pushed towardsthe crankshaft 1300 by the hydraulic pressure on the intake end 1236.

In one embodiment in accordance with the present invention, the fluidused to provide the hydraulic pressure on the right cylinder liner 1230is cooling fluid used to cool the right cylinder liner 1230. Thepressure of the cooling fluid is controlled by a feedback control system(not shown) that controls the position of the cylinder liner 1130, 1230to a predetermined position in accordance with predetermined enginespeed, or other performance parameter.

Engines in accordance with embodiments of the present invention areconfigured to be powered by any number of internal combustion processes,such as, but not limited to, those combustion processes associated withspark ignition (SI), Diesel, and Homogeneous Charge Compression Ignition(HCCI).

In the SI-combustion process, a homogeneous air and fuel mixture iscompressed within the cylinder and ignited at the end of the compressionstroke by a spark. The spark causes a flame kernel, or a heat frontwave, that grows and propagates throughout the combustion chamber.Engine load (torque) is controlled by controlling the rate of flow ofthe air and fuel to the cylinder. The air and fuel ratio is keptsubstantially constant at all loading conditions.

The flame kernel produces a flame front in the cylinder that has atemperature in excess of 1600C, the temperature in which nitrogen-oxides(NOx) are produced. Therefore, some means of mitigating NOx productionis required, such as, but not limited to catalytic conversion to a safercompound.

In an embodiment of the present invention, the cylinder volume isdivided into a combustion chamber and the cylinder, and furthercomprising a NO_(x)-reducing heat sink or a catalytic converter betweenthe combustion chamber and the cylinder (such as provided in PCTapplication number PCT/US 03/08708 entitled ENGINE WITH POWER GENERATINGCAPABILITY, incorporated herein by reference). For reaction kineticreasons, and, in order to maintain the optimum configuration forscavenging, the converter is attached to the exhaust piston; fuel isinjected by spraying directly into the combustion chamber. Such acombustion system offers a breakthrough in extreme low emissioncombustion without sacrificing the fuel consumption, power output orcomfort.

In the Diesel combustion process, pure air is first compressed in thecylinder, causing the air to increase in temperature. Fuel is injectedunder high pressure at the end of the compression stroke, into the hotcompressed air. The fuel is vaporized and mixed partially with thecompressed air. The air and fuel mixture self-ignites when brought to apredetermined temperature. Engine load is controlled by varying theamount of fuel injected into the cylinder.

HCCI is an abbreviation for “Homogeneous Charge Compression Ignition”.The name implies that the homogeneous (“well mixed”) charge of air andfuel is ignited by compression heating.

In the HCCI combustion process, a homogeneous air and fuel mixture iscompressed within the cylinder. As the temperature of the air and fuelmixture is increased due to the increase in pressure, auto-ignitionoccurs. The HCCI combustion process requires a high compression ratio inorder to ensure auto-ignition. A very lean mixture is used in order toslow the chemistry reaction rate, and therefore reduce the combustionrate. Suitable air and fuel mixtures can be achieved by using a high airand fuel ratio or by Exhaust Gas Recycling (EGR). Engine load iscontrolled by varying the amount of fuel in the air and fuel mixture.

The HCCI engine utilizes a high compression ratio and the combustion isfast. This gives a high efficiency at low loads compared to a SI-enginethat has low efficiency at part load.

A major advantage of the HCCI combustion process is that it produces alow amount of nitrogen-oxides (NOx). The formation of NOx is stronglydependent on combustion temperature. Higher temperature produces ahigher amount of NOx. Unlike the high temperature of greater than 1600 Cproduced by the flame front of a SI combustion process producing largeamounts of NOx, the auto-combustion of the HCCI combustion process isinitiated at somewhat less than 1600C, approximately 875 C.

Further, since the combustion is homogeneous and a very lean mixture isused, the combustion temperature becomes very low relative to that of aflame front of a spark-ignition combustion process. This low temperatureresults in very low amounts of NOx being produced. A stoichiometricmixture has an air to fuel ratio of 1. For the HCCI combustion process,the closer the air to fuel ratio is to 1, the higher the ignitiontemperature and the closer to NOx production temperature. Therefore, theHCCI combustion process can be produced using an air to fuel ratio of upto about 10, with the range of 2-10 suitable for producing ignitiontemperatures well below NOx production temperatures.

Further, the HCCI combustion process does not produced the same levelsof soot as the Diesel combustion process.

The HCCI combustion process enables a high thermal efficiency whencompared to other combustion processes because the very fast chemicalreaction in the combustion chamber is very near to the optimal “ConstantVolume Combustion” without the limitation of “knocking.” Knocking is aterm used to define an abnormal combustion condition, also known asdetonation, wherein multiple flame fronts collide inside the combustionchamber, increasing the pressure in the chamber and occurring atinappropriate times during the combustion cycle. Knocking is usually avery undesirable and detrimental condition.

Although embodiments of the present invention can be powered by the HCCIcombustion process, control of the combustion process is more difficultthan in the SI or Diesel combustion process. The HCCI combustion processprovides no direct control of the start of combustion, unlike the sparktiming of a SI combustion process. The start of combustion depends onseveral parameters. The dominant parameters include, among others, thecompression ratio and the inlet temperature. Control of these dominantparameters provides a means to control the start of combustion to adesired point in time.

In accordance with embodiments of the present invention, the engine ispowered by an assisted HCCI combustion process, wherein the air and fuelmixture is compressed within the cylinder to a predetermined state belowthe threshold condition where auto-ignition will occur. An energyassist, such as, but not limited to, a heat source such as produced by,among others, a spark plug or glow-plug, is used to initiate combustionmaintaining a smooth thermal wave combustion condition. The assistedHCCI combustion process works off the threshold condition, producingcontrollable and uniform combustion without the occurrence of anill-timed violent photo-detonation (Knocking).

The energy assist provided for initiating combustion is provided by oneof a number of suitable devices, including, but not limited to, a sparkplug and glow plug. A glow plug has unique advantages as it does notproduce a flame front, unlike the spark plug. A glow plug is a deviceknown in the art that provides a source of rapid heating from an elementthat is exposed to the air and fuel mixture. Glow plugs are well knownfor use in Diesel engines for cold starting. Commonly, upon start-up ofa Diesel engine, the initial temperature of the air and fuel mixture istoo low to sustain auto-ignition. The glow plug provides the neededaddition heat source necessary for combustion. After the engine heats upand can contribute to heating the air and fuel mixture, the glow plug isno longer activated.

In accordance with embodiments of the present invention, a glow plug isprovided in the cylinder and is adapted to control the time of ignitionof the air and fuel mixture. In one embodiment in accordance with thepresent invention, the timing of the heating of the glow plug istriggered by the position of (one of) the pistons. In another embodimentin accordance with the present invention, the timing of the heating ofthe glow plug is triggered by the peak pressure of the air and fuelmixture in the cylinder.

In embodiments in accordance with the present invention, the glow plugis controlled by a feedback control system. The feedback control system,in one embodiment, controls the glow plug timing based on predeterminedperformance criteria. In one embodiment, glow plug heating is timed toproduce combustion ignition when the crankshaft is at TDC, whichprovides the greatest fuel efficiency. In another embodiment, glow plugheating is timed to produce combustion ignition when the combustionchamber reaches peak pressure, typically at 5-10% after TDC.

Further, and in another embodiment, the timing of glow plug heating isdetermined based upon crankshaft performance parameters, such as, butnot limited to, torque variation and angular variation.

In yet anther embodiment, and particularly suitable when constantcrankshaft speeds are desired, such as, but not limited to, electricgeneration applications, glow plug heating is timed to producecombustion ignition to optimize power output.

In other embodiments in accordance with the present invention, thetemperature of the glow plug is variable and controlled for a particularpurpose. By way of example, but not limited thereto, the glow plugtemperature is controlled based& upon the temperature of the air andfuel mixture. In another example, the glow plug temperature iscontrolled based on the temperature of the exhaust fluid. In yet anotherexample, the glow plug temperature is controlled by measured speedoscillations of the crankshaft relative to a desired constant averagespeed of rotation.

Piston Head

Referring again to FIGS. 2 and 3, side cross-sectional views of the leftcylinder 100 in the TDC and BDC positions, respectively, are shown inaccordance with an embodiment of the present invention. Only the leftcylinder 100 is discussed below as the right cylinder 200 comprisessimilar components. The left outer piston 110 comprises a left outerpiston head 116 and a left outer piston plunger 118 opposite the leftouter piston head 116. The left outer piston head 116 terminates at aleft outer piston combustion face 111. The left outer piston head 116 isadapted to be slidingly received in close fitting engagement with theleft cylinder liner bore surface 139 at the left cylinder liner intakeend 136.

The left inner piston 120 comprises a left inner piston head 126 and aleft inner piston push end 124 opposite the left inner piston head 126.The left inner piston head 126 terminates at a left inner pistoncombustion face 121. The left inner piston head 126 is adapted to beslidingly received in close fitting engagement with the left cylinderliner bore surface 139 at the left cylinder liner exhaust end 138.

The left outer piston 110, the left inner piston 120, and the leftcylinder liner 130 define a left combustion chamber 150.

Embodiments of the present invention provide unconventional design ofthe shape of the left outer piston combustion face 111 and left innerpiston combustion face 121, and therefore the overall shape of the leftcombustion chamber 100, because there are no valves. FIG. 12 is a sidecross-sectional view of the left cylinder 100 including a left outerpiston combustion face 111 and left inner piston combustion face 121near top dead center forming a torroidal combustion chamber 1150 a, inaccordance with an embodiment of the present invention, as firstpresented in PCT/US00/34122 entitled INTERNAL COMBUSTION ENGINE WITH ASINGLE CRANKSHAFT AND HAVING OPPOSED CYLINDERS WITH OPPOSED PISTONS,incorporated herein by reference. The combustion chamber 1150 a isformed by the left outer piston combustion face 111 having a convextorroidal shape matching the left inner piston combustion face 121 witha complimentary profile. The left outer and inner piston combustionfaces 111, 121 form a broad area squish band that creates a swirl ofhigh intensity near top dead center providing the potential for improvedexhaust emissions, and also fuel consumption, power output and comfortOther shapes of the left outer piston combustion face 111 and left innerpiston combustion face 121 are anticipated, suitable for a particularpurpose.

FIG. 13A is a side cross-sectional view of the left cylinder 100comprising the left outer piston head 116 including a left outer pistoncombustion face 111 and a spark igniter 180, such as, but not limited toa conventional spark plug known in the art, in accordance with anembodiment of the present invention. The spark igniter 180 is disposedwithin the left outer piston head 116 such that a spark gap 182 issuitably located adjacent the outer piston combustion face 111 andsuitably exposed to the intake fluid.

It is understood that the spark igniter 180 could be located on othercomponents of the left cylinder 100, such as, but not limited to, theleft inner piston combustion face 121 and integrated into the side ofthe left cylinder liner 130.

FIGS. 13A and 13B are partial cross-sectional views of the left cylinder100 comprising an intermittent-contact spark ignition system 185 in adisengaged and engaged position, respectively, in accordance with anembodiment of the present invention. The intermittent-contact sparkignition system 185 comprises a moving contact 186 extending from theleft outer piston 110, and a stationary contact 188 in opposedrelationship and in axial alignment to the moving contact 186. Themoving contact 186 and the stationary contact 188 come into electricalcontact creating an electric discharge at the spark gap 182 when theleft outer piston head 116 moves substantially to the TDC position. Themoving contact 188 and the stationary contact 186 move apart out ofelectrical contact at all other positions of the left outer piston 110.

In an embodiment of the present invention, the spark tiring isadjustable by adjusting the relative axial position of the stationarycontact 188. An earlier spark timing is obtained by moving thestationary contact 188 closer to the moving contact 186, whereas aretarded spark timing is obtained by moving the stationary contact 188further away from the moving contact 186.

FIG. 14 is a partial cross-sectional view of the left cylinder 100comprising a sliding-contact ignition system 285, in accordance with anembodiment of the present invention. As in the embodiment of FIG. 11A,above, an ignition source, such as a spark igniter 180 or a glow plug280 as shown, is disposed within the left outer piston head 116. Thesliding-contact ignition system 285 comprises a receiving contact 286extending from the glow plug 280 to the left outer piston plunger 118and a sliding contact 288 extending from the left housing end cap 107and in axial alignment with the receiving contact 286. The receivingcontact 286 provides a surface 287 for nesting engagement with thesliding contact 288.

The receiving contact 286 and the sliding contact 288 remain inelectrical contact throughout the stroke movement of the left outerpiston 110, the sliding contact 288 sliding within the receiving contact288. In the case of the ignition source being a spark igniter 180, thespark igniter 180 is controlled in the conventional manner that when theleft outer piston head 116 moves substantially to the TDC position, thespark igniter 180 is caused to create an electric discharge at the sparkgap 182. In the case of the glow plug 280, the heating of the glow plug280 can be controlled at any portion of the piston cycle. For example,but not limited to, the glow plug 280 can be controlled to heat theintake fluid to a predetermined temperature during scavenging, whereasit is controlled to produce a high temperature surge at TDC. I otherwords, a glow plug 180 can be operated continuously to heat the intakefluid, whereas the spark plug 180 can only be used for ignition.

In accordance with an embodiment of the present invention, the sparkigniter 180 as shown in FIG. 13A is replaced with a glow plug 280. Theglow plug 280 provides a source of heat that augments the self ignitionof the intake fluid under pressure. As the pressure and therefore thetemperature of the intake fluid raises during the compression phase ofthe cycle, the glow plug 280 is activated to provide a source of heat tothe intake fluid so as to assist the intake fluid to self ignite at apredetermined time in the cycle.

The glow plug 280 does not have to operate at the extreme temperature asthat of an electric discharge in order to provide conditions for selfignition of the intake fluid. By way of example, during engine startupthe intake fluid is relatively cool, wherein the glow plug 280 raisesthe intake fluid temperature sufficient that with additional compressionof the intake fluid at TDC, the temperature of the intake fluid issufficient to sustain self ignition. Further, the relativelylow-temperature ignition of the intake fluid about the glow plug 280acts to provide a pressure source, much like a piston, compressing theintake fluid further and raising the fluid temperature to above theself-ignition temperature, causing a uniform combustion of the intakefluid throughout the left combustion chamber 1150.

Ideally, for performance and emissions considerations, among others,combustion of the intake fluid within the left combustion chamber 1150should occur uniformly, spontaneously, and completely. Spark ignitiontypically, and in some cases glow-plug ignition, produces non-uniformcombustion of the intake fluid. A flame front can be produced thatadvances through the combustion chamber producing non-uniform andnon-complete combustion of the intake fluid. The detrimental effects ofthe flame front is reduced in embodiments of the present inventionwherein self ignition conditions are provided in the combustion chamberand ignition by a spark or glow plug occurs at about the self ignitionconditions.

Other embodiments in accordance with the present invention are providedto minimize or eliminate non-uniform and non-complete combustion. Theseembodiments include, but are not limited to, contained ignition within acavity or chamber of a piston. FIGS. 15A-15C are side cross-sectionalviews of embodiments of left outer piston heads 116 a-c wherein the glowplug 280 is provided in a cavity formed in the left outer piston head116 a-c extending from the left inner piston combustion face 121 a-c, inaccordance with embodiments of the present invention. The glow plug 280extends into the cavity to heat the intake fluid contained therein. Inthis arrangement, any flame front that potentially can be produced bythe glow plug 280 is substantially contained within the cavity for atleast the time it takes for self ignition to take place outside of thecavity. The benefit of a pressure increase of the intake fluid outsideof the cavity caused by the ignition of the intake fluid within thecavity is realized to produce a uniform raise in pressure andtemperature for uniform, spontaneous and complete combustion within theleft combustion chamber 1150.

FIG. 15A is a partial side cross-sectional view of a left outer pistonhead 116c wherein the glow plug 180 extends into a spherical cavity 190formed in the left outer piston head 116 a extending from the left innerpiston combustion face 121 a, in accordance with an embodiment of thepresent invention. The spherical cavity 190 comprises an inlet port 191that is adapted to direct incoming intake fluid into the sphericalcavity 190 but is sufficiently small so as to substantially contain anyflame front.

FIG. 15B is a partial side cross-sectional view of a left outer pistonhead 116 b wherein the glow plug 180 extends into a swirl cavity 192formed in the left outer piston head 116 b extending from the left innerpiston combustion face 121 b, in accordance with an embodiment of thepresent invention. The swirl cavity 192 comprises an inlet port 193 thatis adapted to direct incoming intake fluid to flow adjacent the swirlcavity surface 194 and to be substantially retained within the swirlcavity 192. The glow plug 280 extends into the swirl cavity 192 and ispositioned out of the line of sight of the inlet port 193. In thisarrangement, any flame front that is potentially produced by the glowplug 280 is directed to the swirl cavity surface 194 opposite the glowplug 280 to reflect there-and-back-again substantially delaying the timein which it may exit the swirl cavity 192.

FIG. 15C is a partial side cross-sectional view of a left outer pistonhead 116 c wherein the glow plug 280 extends into a cavity bottom 197 ofan elongated cavity 196 formed in the left outer piston head 116 cextending from the left inner piston combustion face 121 c, inaccordance with an embodiment of the present invention. The elongatedcavity 196 comprises an inlet end 195 that is adapted to direct incomingintake fluid to the cavity bottom 197. The depth of the elongated cavity196 is predetermined such that any flame front produced by the glow plug280 will not exit the elongated cavity 197 until the self ignition ofthe intake fluid outside of the elongated cavity 196.

In other embodiments in accordance with the present invention, thecavity, such as the elongated cavity 196 shown in FIG. 15C, amongothers, comprises an inner surface 198 at least a portion of whichhaving a catalytic layer 199 thereon. In an embodiment, the catalyticlayer 199 comprises a material that reduces the quantity of NOx or otherundesirable emission that might be formed by a flame front producedwithin the elongated cavity 196. In another embodiment, the catalyticlayer 199 comprises a material that reduces the potential formation of aflame front produced within the elongated cavity 196.

In other embodiments in accordance with the present invention, theheating element of the glow plug 280 further comprises a catalyticmaterial 299. The catalytic material 299 comprises a material thattriggers combustion based on the chemistry of the intake fluid. As theintake fluid pressure rises, ignition is triggered when a predeterminedconcentration of constituent compounds within the intake fluid isreached.

It is understood that in embodiments of ignition systems presentedabove, among others, spark igniters 180 and glow plugs 280, amongothers, may be used interchangeably. By way of example, the sparkigniter 180 shown in FIG. 13A can be replaced by the glow plug 280 asshown in FIG. 14.

Fuel Supply Systems

Fuel is supplied to embodiments of engines in accordance with thepresent invention in a variety of ways. Referring again to FIG. 9, afuel injector 1183 is provided adjacent each left/right cylinder liner1130, 1230 terminating with a fuel injector port 1184 and in fluidcommunication with the left/right combustion chamber 1150, 1250, inaccordance with an embodiment of the present invention. Intake fluid inthe form of air enters the left/right combustion chamber 1150, 1250through the left/right intake ports 1161, 1261. Fuel is injected in theleft/right combustion chamber 1150, 1250 at a suitable time in as theintake fluid is under compression.

Referring again to FIGS. 13A and 13B, a fuel injector 183 is provided influid communication with the second scavenging chamber 109. Intake fluidin the form of air is provided from the first scavenging chamber 105 tothe second scavenging chamber 109 which is mixed with fuel provided bythe fuel injector 109. A fuel and air mixture is provided to thecombustion chamber 150 through the intake ports 161 from the secondscavenging chamber 109.

Crankshaft

FIG. 16 is a top exploded cross-sectional view of the crankshaft 300,left and right pullrods 411 a,b, 421 a,b and left and right pushrods412, 422, in accordance with an embodiment of the present invention.FIG. 17 is an assembled top view of the assembly of FIG. 16. Thecrankshaft 300 is referred to as a “built-up” crankshaft. In contrast toa single forging of a conventional engine crankshaft, embodiments of thecrankshaft 300 of the present invention comprise an assembly of fourcomponents, a first crankshaft component 320, a second crankshaftcomponent 330, a third crankshaft component 340, and a fourth crankshaftcomponent 350, that are coupled together to form a single crankshaft300.

The first crankshaft component 320 comprises a cylindrical first mainbearing 325 including a first through bore 323 that defines a crankshaftrotation axis 310. The first crankshaft component 320 further comprisesa first nesting surface 322 that has a first offset axis 321 that isoffset from the crankshaft rotation axis 310. The first main bearing 325provides support between the crankshaft 300 and the housing 103, asshown in FIG. 1.

The second crankshaft component 330 comprises a second through bore 333that is coaxial with the first through bore 323 and also defines thecrankshaft rotation axis 310. The second crankshaft component 330furthers comprises a second nesting surface 332 that has a second offsetaxis 331 that is offset from the crankshaft rotation axis 310, and athird nesting surface 336 having a third offset axis 337 that is offsetfrom both the crankshaft rotation axis 310 and the second offset axis331. The first nesting surface 322 is adapted to be slidingly receivedinto the second nesting surface 332. The second crankshaft component 330further comprises a first bearing surface 334 having a cylindricalcross-section and coaxial with the second offset axis 331. The firstbearing surface 334 is adapted to accept a first ring bearing 361thereon, which will be further described below.

The third crankshaft component 340 comprises a third through bore 343that is coaxial with the first through bore 323 and also defines thecrankshaft rotation axis 310. The third crankshaft component 340 furthercomprises a fourth nesting surface 342 that has a fourth offset axis 347that is offset from the crankshaft rotation axis 310 and coaxial withthe third offset axis 337. The third nesting surface 336 is adapted tobe slidingly received into the fourth nesting surface 342. The thirdcrankshaft component 340 further comprises a second bearing surface 344having a cylindrical cross-section and is coaxial with the fourth offsetaxis 349. The second bearing surface 344 is adapted to accept a secondring bearing 362, which will be described below.

The third crankshaft component 340 further comprises a fifth nestingsurface 346 that has a fifth offset axis 341 that is offset from thecrankshaft rotation axis 310 and coaxial with the second offset axis331. The third crankshaft component 340 further comprises a thirdbearing surface 348 having a cylindrical cross-section. The thirdbearing surface 348 is adapted to accept a third ring bearing 363thereon, which will be further described below.

The fourth crankshaft component 350 comprises a cylindrical second mainbearing 355 including a fourth through bore 353 that is coaxial with thefirst through bore 323 and also defines the crankshaft rotation axis310. The fourth crankshaft component 350 further comprises a sixthnesting surface 352 that has a sixth offset axis 351 that is offset fromthe crankshaft rotation axis 310 and coaxial with the fifth offset axis341, which is also coaxial with the first and second offset axes 321,331. The third bearing surface 348 of the third crankshaft component 340is coaxial with the sixth offset axis 351. The sixth nesting surface 352is adapted to be slidingly received into the fifth nesting surface 346.The second main bearing 355 provides support between the crankshaft 300and the housing 103, as shown in FIG. 1.

It is understood that there are many different possible arrangements ofnesting surfaces and bearing surfaces wherein the above embodiment isjust one of those possible arrangements and is not limited thereto.Other possible arrangements are also anticipated.

In an embodiment in accordance with the present invention, therespective nesting surfaces are adapted to allow for a press-fitassembly with sufficient fastness to remain in axial and angularalignment, but allowing for disassembly. In another embodiment, therespective nesting surfaces have keys and key ways to ensure properaxial and angular alignment.

Pushrods

The two pair of left and right pullrods 411 a,b, 421 a,b and the pair ofleft and right pushrods 412, 422 are the connecting elements between thepistons and the crankshaft 300, as shown in FIGS. 16 and 17, inaccordance with an embodiment of the invention. The linear reciprocationof the pistons drive the connecting elements to impart rotational motionto the crankshaft 300.

FIG. 18 is an isometric exploded view of the left and right pushrods412, 422, the second and third crankshaft components 330, 340, and thesecond roller bearing 362, in accordance with an embodiment of thepresent invention. The left and right pushrods 412, 422 resistcompressive forces by the left and right inner piston 120, 220 asprovided earlier and shown in FIG. 1, and are therefore termed“pushrods.” As shown in FIGS. 1, 16-18, the left and right pushrods 412,422 are disposed on a common inner piston journal 312, also referredherein as a pushrod journal, on the crankshaft 300.

In embodiments in accordance with the present invention, the left andright pushrods 412, 422 lie in a common plane. An embodiment thatpermits coplanar alignment of the left and right pushrods 412, 422comprises the left pushrod 412 having a single aperture journal end 414opposite the left concave end 413. The single aperture journal end 414has a single aperture 415 that is adapted to rotatably engage around thesecond ring bearing 362 in close-fitting engagement.

The right pushrod 422 comprises a double aperture journal end 424opposite the right concave end 423. The double aperture journal end 424comprises a pair of tangs 426, also referred to as a fork, each with acoaxial aperture 425 that is adapted to rotatably engage around thesecond ring bearing 362 in close-fitting engagement. The tangs 426 arespaced-apart a predetermined distance to slidably receive the singleaperture journal end 414 of the left pushrod 412.

The left and right pushrods 412, 422 are assembled onto the crankshaft300 by receiving the single aperture journal end 414 of the left pushrod412 between and in coaxial alignment with the pair of coaxial apertures425 of the double aperture journal end 424 of the right pushrod 422. Thesecond ring bearing 362 is slidably received within the single aperture415 and coaxial apertures 425. The fourth nesting surface 342 of thethird crankshaft component 340 is disposed within the second ringbearing 362. The third nesting surface 336 of the second crankshaftcomponent 330 is disposed within the fourth nesting surface 342 of thethird crankshaft component 340 completing the assembly. The left andright pushrods 412, 422 now share a common journal of the crankshaft300, and therefore, a common journal 312.

The above embodiment is characterized by the elimination of bolts orother fasteners, increasing component reliability and performance.

In one embodiment of the present invention, the left and right pushrods412, 422 have a ratio of length divided by crankshaft radius of about 5.This relatively large ratio results in much lower side forces andfrictional loss between the inner pistons 120, 220 and the cylinderliner bore surface 139, 239, as compared to conventional engines.Typical prior art ratios are in the range of 3.2 to 3.8.

Pullrods

The pair of left and right pullrods 411 a,b, 421 a,b resist tensileforces by the left and right outer piston 110, 210 as provided earlierand shown in FIG. 1, and are therefore termed “pullrods.” As shown inFIGS. 1, 16 and 17, the left and right pullrods 411 a,b, 421 a,b aredisposed on a common pair of outer piston journals 311 a,b, alsoreferred herein as a pullrod journals, on the crankshaft 300.

In embodiments in accordance with the present invention, the left andright pullrods 411 a,b, 421 a,b lie in a common plane. The embodimentthat permits coplanar alignment of the left and right pushrods 412, 422as provided above serves to also permit coaxial alignment of the leftand right pullrods 411 a,b, 421 a,b. In an embodiment, the left pullrods411 a,b have a single aperture journal end 416. The single aperturejournal end 416 has a single aperture 417 that is adapted to rotatablyengage around one of the first and third ring bearings 361, 363 inclose-fitting engagement.

The right pullrods 421 a,b comprise a double aperture journal end 426.The double aperture journal end 426 comprises a pair of tangs 428 eachwith a coaxial aperture 427 that is adapted to rotatably engage aroundone of the first and third ring bearings 361, 363 in close-fittingengagement. The tangs 428 are spaced-apart a predetermined distance toslidably receive the single aperture journal end 416 of the left pullrod411 a,b.

The left and right pullrods 41 la,b, 421 a,b are assembled onto thecrankshaft 300 by receiving the single aperture journal end 416 of theleft pullrod 411 a,b between and in coaxial alignment with the pair ofcoaxial apertures 427 of the double aperture journal end 426 of theright pullrods 421 a,b. One of the first and third ring bearings 361,363 is slidably received within the single aperture 417 and coaxialapertures 427. The second nesting surface 332 of the second crankshaftcomponent 330 is disposed within the first ring bearing 361. The firstnesting surface 322 of the first crankshaft component 320 is disposedwithin the second nesting surface 332 of the second crankshaft component330 completing the assembly. One pair of the left and right pullrods 411a, 421 a now share a common journal of the crankshaft 300.

Similarly, the fifth nesting surface 346 of the third crankshaftcomponent 340 is disposed within the third ring bearing 363. The sixthnesting surface 352 of the fourth crankshaft component 350 is disposedwithin the fifth nesting surface 346 of the third crankshaft component340 completing the assembly. The other pair of left and right pullrods411 b, 421 b now share a common journal of the crankshaft 300, andtherefore, a common journal 311 a,b.

The above embodiment is characterized by the elimination of bolts orother fasteners, increasing component reliability and performance.

In embodiments of the present invention provide relatively long left andright pullrods 411 a,b, 421 a,b. The ratio between the length of theleft and right pullrods 411 a,b, 421 a,b and the crankshaft radius isgreater than about 10. This configuration results in much lower sideforces and friction between the outer pistons 110, 120 and the cylinderliner bore surface 139, 239, than is typical of known art.

FIG. 19 is an isometric assembled view of a crankshaft 300, inaccordance with an embodiment of the present invention. The first,second, and third ring bearings 361,362, 363 described above provide forfriction reduction between the journal ends 416, 426, 414, 424 of theleft and right pullrods 41 la,b, 421 a,b and left and right pushrods412, 422 and the respective bearing surfaces 334, 344, 348 of thecrankshaft 300. The first, second, and third ring bearings 361, 362, 363are shown by way of example and not limited thereto. It is anticipatedthat other types of friction reduction components and/or methods can beutilized, such as, but not limited to, needle bearings, roller bearings,lubricious coatings and circulating lubrication fluids.

The built-up crankshaft 300, as shown in FIGS. 1, 16 and 17 by way ofexample, enables the connecting elements, such as the left and rightpullrods 41 la,b, 421 a,b and left and right pushrods 412, 422, alongwith any associated bearing member, to be pre-assembled. This avoidsconnecting elements found in the known art such as split connecting rodsand split-bearings. Split connecting rods require support structure andfasteners so that they may be assembled to form a one-piece crankshaft.These are eliminated in the present embodiments.

The built-up crankshaft 300, in accordance with embodiments of thepresent invention, consists of several individual components that aresubsequently assembled. The generally smaller individual componentsoffer advantages in the manufacturing process, for example, forging,machining, finishing, and other secondary work. Also, the built-upcrankshaft 300 offers the advantage of lighter weight. Because theconnecting elements do not require fasteners, simpler elements of lowermass may be used. Moreover, the assembly of the several components maybe accomplished during insertion of the crankshaft 300 into the housing103, for example.

Another characteristic of the present embodiments is that a built-upcrankshaft 300 can be used because there is a reduction of forceexperienced by the crankshaft 300. The balanced nature of thereciprocating components on the engine, and the elimination ofunbalanced combustion forces, provides substantially no resultant forceon the main bearings 325, 355 supporting the crankshaft 300. Contrary tothe known art where literally tons of unbalanced forces are exerted onthe crankshaft, the present embodiments have substantially no unbalancedforces. This reduction in forces includes a reduction on the crankshaftmain bearings 325, 355 and the engine assembly in general.

In a known conventional in-line or “V”-engine, torque is created byuneven forces on the main bearing and the crankshaft. In the presentembodiments, these forces are substantially eliminated, and only twomain bearings 325, 355, and no center main bearing, are necessary tosupport the crankshaft 300 in the housing 103.

Due to the configuration of the various components contemplated in thepresent embodiments, the crank radius may be only about half of that ofa conventional design with a similar piston stroke. In part, the crankradius as defined by the crankcase perpendicular to the cylinder axis,is reduced due to the split throw of the overall piston stroke.

FIG. 20 is a cross-sectional isometric assembled view of the crankshaft300 of FIG. 19, in accordance with an embodiment of the presentinvention. The first, third, and fourth crankshaft components 320, 340and 350 further comprise first, second, and third fluid channels 329,339, 359, respectively. The first, second, and third fluid channels 329,339, 359 provide means for fluid, such as, but not limited to,lubricating and cooling fluid, to readily pass through the crankshaftcavity 304, as shown in FIG. 1. The crankshaft 300 further comprisesbearing lubrication passages 335, 345, 349 adapted to provide fluid,such as, but not limited to, lubricating and cooling fluid, directly tothe first, second, and third bearing surfaces 334, 344,348,respectively.

The primary role of the crankshaft is to convert the reciprocatingmotion of the pistons, as conveyed through the pullrods and pushrods,into rotational motion. Unbalanced forces acting on a crankshaft resultin increased friction between the crankshaft and its supportingbearings. The existence of unbalanced forces also complicates enginedesign, since the forces must somehow be mechanically transferred to thesupporting structure of the engine, which must be sufficiently sturdy toaccommodate the forces. In a standard four cylinder in-line engine, forexample, the forces from all four pistons act in the same directionagainst the crankshaft, and literally tons of pressure must betransferred through the crankshaft main bearings to the enginestructure. A typical four cylinder in-line engine will have five mainbearings supporting the crankshaft.

Embodiments of engines in accordance with the present invention allowfor simpler crankshaft designs, since the reactive forces of the innerand outer pistons in each cylinder is substantially cancelled. Referringto the left cylinder 100 as illustrated in FIG. 1, it can be seen thatsince the compression and combustion forces acting on the inner andouter pistons 120, 110 will be substantially equal and opposite, thepullrods 411 of the outer pistons 110 will pull against the crankshaft300 with substantially the same force with which the pushrod 412 of theinner piston 120 pushes. The result will be a turning moment on thecrankshaft 300, with only very minor unbalanced side-to-side andup-and-down forces due to the slightly different angles of the pullrods411 and pushrods 412, and the asymmetrical timing of the pistons. Theloads on the crankshaft main bearings 325, 355 are therefore very small,which eliminates the need for any center main bearings and results inmuch lower friction losses than in an in-line four cylinder engine ofcomparable performance.

FIG. 21 is a partial cutaway isometric view of an engine 14, inaccordance with an embodiment of the present invention. The engine 14comprises a housing 1103 containing a left cylinder 1100, an axiallyaligned right cylinder 1200 opposite the left cylinder 1100, and acrankshaft 1300 located there between. The crankshaft 1300 comprises acrankshaft first end 1306 and a crankshaft second end 1307. Coupled toeach of the crankshaft first and second ends 1306, 1307 is a balancingsystem 500 described below.

FIG. 22 is a partial cut-away view of a balancing system 500 comprisinga balancing system housing 514, a counter weight 508, and a planetarygear assembly 506, in accordance with an embodiment of the presentinvention. The balancing system housing 514 is adapted to be coupled tothe engine housing 1103 with mounting fasteners 512, described below.The planetary gear assembly 506 comprises a crank shaft gear 518 and acounter-rotating gear 519. The counter weight 508 includes a shaftaperture 516 that is adapted to be placed coaxial with the crank shaft1300 and free to rotate about the crank shaft axis 310. The crank shaftgear 518 is adapted to be coaxial with, coupled to, and driven by thecrank shaft 1300, and adapted to engage the counter-rotating gear 519.The counter-rotating gear 519 is coupled to the counter weight 508. Byway of example, the crank shaft 1300 drives the crank shaft gear 518 ina counter clockwise direction. The crank shaft gear 518, in turn, drivesthe counter rotating gear 519 in a clockwise direction which drives thecounter weight 508 in a clockwise direction.

The balancing system 500 is suitable for substantially counter-actingagainst the minor unbalanced first-order sinusoidal side-to-side andup-and-down forces due to the slightly different angles of the pullrods411 and pushrods 412 on the crank shaft 1300, and the asymmetricaltiming of the pistons. The counter weight 508 is positioned on the crankshaft axis 1300 at a predetermined angle to substantially counter actthe unbalanced forces.

Approximately 50% of all friction losses in an engine come from lateralforces produced by the movement of the pullrods 411 and pushrods 412rotating in their respective journals, acting on the piston, i.e.,pushing the pistons against the cylinder liner bore surface 1139, 1239.A short connecting rod produces high lateral forces while a longconnecting rod produces low lateral forces (an infinitely longconnecting rod would produce no lateral forces on the piston at all, butit would also be infinitely large and infinitely heavy). It is desiredto reduce these lateral forces and therefore friction losses without anincrease in connecting rod size or weight.

Referring again to FIG. 9, the pushrods 1412, 1422 are subject only tocompression loads that eliminate a need for a wrist pin. This isreplaced by a concave end 1413, 1423 of large diameter that slides on amating convex surface 1125, 1225.

Referring again to FIG. 3, the left and right pullrods 411, 421 arecoupled to the left and right outer pistons 110, 210 by means of leftand right bridges 170, 270. FIG. 23 is a cross sectional view along thecut line 23-23 of FIG. 3 showing the left bridge 170 comprising a bridgeconcave surface 173 that is adapted to be slidingly received in convexpull surface 172 of the right outer piston 210, in accordance with anembodiment of the present invention. A bridge bearing 372 is used, suchas a needle bearing, to reduce the friction between the bridge concavesurface 173 and the convex pull surface 172.

Engine with Fluid Dynamic Effect

Again, FIG. 21 is a partial cutaway isometric view of an engine 14 inaccordance with another embodiment of the present invention. The engine14 comprises a housing 1103 containing a left cylinder 1100, an axiallyaligned right cylinder 1200 opposite the left cylinder 1100, and acrankshaft 1300 located there between. FIG. 21 depicts the engine 14 ata crankshaft angle of 270° after TDC of the left cylinder.

The left cylinder 1100 comprises a left cylinder liner 1130, a leftouter piston 1110 and a left inner piston 1120. The left cylinder liner1130 comprises a left cylinder liner outer surface 1132 and a boredefining a left cylinder liner bore surface 1139. The left cylinderliner 1130 further comprises a left cylinder liner intake end 1136 and aleft cylinder liner exhaust end 1138. The left cylinder liner intake end1136 comprises a plurality of left intake ports 1161 and the leftcylinder liner exhaust end 1138 comprises a plurality of left exhaustports 1163, which will be further described below.

The left outer piston 1110 comprises a left outer piston head 1116 and aleft outer piston plunger 1118 opposite the left outer piston head 1116.The left outer piston head 1116 terminates at a left outer pistoncombustion face 1111. The left outer piston head 1116 is adapted to beslidingly received in close fitting engagement with the left cylinderliner bore surface 1139 at the left cylinder liner intake end 1136.

The left inner piston 1120 comprises a left inner piston head 1126 and aleft inner piston push end 1124 opposite the left inner piston head1126. The left inner piston head 1126 terminates at a left inner pistoncombustion face 1121. The left inner piston head 1126 is adapted to beslidingly received in close fitting engagement with the left cylinderliner bore surface 1139 at the left cylinder liner exhaust end 1138.

The left outer piston 1110, the left inner piston 1120, and the leftcylinder liner 1130 define a left combustion chamber 1150.

Similarly, the right cylinder 1200 comprises a right cylinder liner1230, a right outer piston 1210 and a right inner piston 1220. The rightcylinder liner 1230 comprises a right cylinder liner outer surface 1232and a bore defining a right cylinder liner bore surface 1239. The rightcylinder liner 1230 further comprises a right cylinder liner intake end1236 and a right cylinder liner exhaust end 1238. The right cylinderliner intake end 1236 comprises a plurality of right intake ports 1261and the right cylinder liner exhaust end 1238 comprises a plurality ofright exhaust ports 1263, which will be further described below.

The right outer piston 1210 comprises a right outer piston head 1216 anda right outer piston plunger 1218 opposite the right outer piston head1216. The right outer piston head 1216 terminates at a right outerpiston combustion face 1211. The right outer piston head 1216 is adaptedto be slidingly received in close fitting engagement with the rightcylinder liner bore surface 1239 at the right cylinder liner intake end1236.

The right inner piston 1220 comprises a right inner piston head 1226 anda right inner piston push end 1224 opposite the right inner piston head1226. The right inner piston head 1226 terminates at a right innerpiston combustion face 1221. The right inner piston head 1226 is adaptedto be slidingly received in close fitting engagement with the rightcylinder liner bore surface 1239 at the right cylinder liner exhaust end1238.

The right outer piston 1210, the right inner piston 1220, and the rightcylinder liner 1230 define a right combustion chamber 1250.

The left outer piston 1.110 and the right outer piston 1210 are coupledto a pair of common journals, outer piston journals 1311, on thecrankshaft 1300. The left inner piston 1120 and the right inner piston1220 are coupled to a common journal, an inner piston journal 1312. Thecrankshaft 1300 will be further described below.

The left outer piston 1110 of the left cylinder 1100 is coupled to thecrankshaft 1300 by means of a pair of left pullrods 1411, one on eitherside of the cylinder 1100. Similarly, the right outer piston 1210 of theright cylinder 1200 is coupled to the crankshaft 1300 by two rightpullrods 1421. The left and right pullrods 1411, 1421 are coupled to theleft and right outer pistons 1110, 1210 by means of bridges 1170, 1270that ride on convex surfaces 1172, 1272 on the left and right outerpistons 1110, 1210.

The left inner piston 1120 of the left cylinder 1100 is coupled to thecrankshaft 1300 by means of a left pushrod 1412; the right inner piston1220 of the right cylinder 1200 is similarly coupled to the crankshaft1300 by a right pushrod 1422. The left/right pushrods 1412, 1422 haveleft/right concave ends 1413, 1423 that ride on left/right convexsurfaces 1125, 1225 on the left/right inner piston push ends 1124, 1224of the left/right inner pistons 1120, 1220, respectively. The left/rightpushrods 1412, 1422 and the left/right convex surfaces 1125, 1225 willbe further described below.

The four pistons 1110, 1120, 1210, and 1220 have a plurality of pistonrings 1112, 1122, 1212, and 1222, respectively, located both behind thecombustion faces 1111, 1121, 1211, 1221 and further along the pistonheads 1116, 1118, 1216, 1218 to prevent the escape of fluid from betweenthe piston heads 1116, 1118, 1216, 1218 and the bore surface 1115, 1215.

The housing 1103 is adapted to house the left cylinder 1100, the rightcylinder 1200, and the crankshaft 1300. The housing 1103 comprises aleft cylinder cavity 1104, a right cylinder cavity 1204, and acrankshaft cavity 1304, adapted to house the left cylinder 1100, theright cylinder 1200, and the crankshaft 1300, respectively. The leftcylinder cavity 1104 defines a left plunger bore surface 1106 andterminates with a left housing end cap 1107. The left plunger 1107 isadapted to be slidingly received in close fitting engagement with theleft plunger bore surface 1106. The left plunger 1107, the left housingend cap 1107, and the left plunger bore surface 1106 define a first leftscavenging chamber 1105.

The left cylinder cavity 1104, the left plunger 1107, the left cylinderliner 1130, and the crankshaft 1300 define a second left scavengingchamber 1109. The second left scavenging chamber 1109 is in open fluidcommunication with the crankshaft cavity 1304 permitting flow of fluidfreely there through.

Similarly, the right cylinder cavity 1204 defines a right plunger boresurface 1206 and terminates with a right housing end cap 1207. The rightplunger 1207 is adapted to be slidingly received in close fittingengagement with the right plunger bore surface 1206. The right plunger1207, the right housing end cap 1207, and the right plunger bore surface1206 define a first right scavenging chamber 1205.

The right cylinder cavity 1204, the right plunger 1207, the rightcylinder liner 1230, and the crankshaft 1300 define a second rightscavenging chamber 1209. The second right scavenging chamber 1209 is inopen fluid communication with the crankshaft cavity 1304 permitting flowof fluid freely there through. Consequently, therefore, the second leftscavenging chamber 1109, the crankshaft cavity 1304 and the second rightscavenging chamber 1209 are in open fluid communication permitting flowof fluid freely there between.

The free-flow of fluid between the second left scavenging chamber 1109,the crankshaft cavity 1304 and the second right scavenging chamber 1209provides a fluid dynamic effect of the fluid contained within. Thisfluid dynamic effect has the effect of preferentially increasing thepressure of the scavenging fluid at the opportune time during theopening phase of the left and right intake ports 1161, 1261. Adescription of a engine cycle will explain this effect more clearly.

Assume that the left cylinder 1100 is undergoing a power stroke whereinthe crankshaft 1300 is at “bottom dead center” (BDC). During the powerstroke, the left outer piston 1110 and the left inner piston 1210 aredriven apart by the high pressure fluid within the left combustionchamber 1150 produced during combustion. The left outer piston 1110 andthus the left outer piston plunger 1118 is driven towards the lefthousing end cap 1107, which in turn decreases the volume, and increasesthe pressure, within the first left scavenging chamber 1105. At apredetermined pressure, a one-way valve 168 (See FIG. 3) within the leftouter piston plunger 1118 releases high-pressure fluid from the firstleft scavenging chamber 1105 into the second left scavenging chamber1109. At a predetermined time during the high-pressure fluid releasefrom the first left scavenging chamber 1105, the left intake ports 1161are opened to permit high pressure fluid to enter the left combustionchamber 1150.

Simultaneously with the initiation of the power stroke of the leftcylinder 1100, the right cylinder 1200 undergoes the initiation of acompression stroke. During the compression stroke, the right outerpiston 1210, and thus, the right outer piston plunger 1218 are driventowards the direction of the crankshaft 1300, and thus the left cylinder1100. This has the effect of compressing the fluid contained within thesecond right scavenging chamber 1209, driving the fluid through theright intake ports 1261 when open, as well as driving the fluid throughthe crankshaft chamber 1304 and into the second left scavenging chamber1109, raising the pressure within the second left scavenging chamber1109.

The fluid pressure wave created by the forward momentum of the fluidwithin the second right scavenging chamber 1209 arrives in the secondleft scavenging chamber 1109 as the left outer piston 1110 moves in thecompressive stroke toward the crankshaft 1300, and while the left intakeports 1161 are open, even as the right outer piston 1210 begins to movein the opposite direction away from the crankshaft 1300, closing theleft exhaust ports 163 and further compressing the intake fluid in theleft combustion chamber 150. This fluid pressure wave arrives at theopen left intake ports 1161 effectively increasing the pressure of theintake fluid for scavenging.

FIG. 24 is a schematic top view of an engine 13 comprising a pluralityof OPOC engines 11, shown herein with four engines 11, coupled to acommon crankshaft 300 having an axis 310 in side-by-side parallelrelationship, in accordance with an embodiment of the present invention.Engines 13 of this configuration are characterized by simply couplingadditional engines 11 to the common crankshaft 300 for providingadditional power output in a relatively flat profile package.

FIG. 25 is a schematic front view of an engine 16 comprising a pluralityof an odd number of OPOC engine cylinders 15, shown herein with threeengine cylinders 15, coupled to a common crankshaft 300 in anequally-spaced radial relationship, in accordance with an embodiment ofthe present invention. Engines 16 of this configuration arecharacterized by simply coupling additional engine cylinders 15 to thecommon crankshaft 300 for providing additional power output. In otherembodiments, additional engines 16 are coupled to the common crankshaft300 in a parallel relationship, such as shown in FIG. 24.

FIG. 26 is a schematic front view of an engine 18 comprising a pluralityof OPOC engines 11, shown herein with two engines 11, coupled to acommon crankshaft 300 in an equally-spaced radial relationship, inaccordance with an embodiment of the present invention. Engines 18 ofthis configuration are characterized by simply coupling additionalengines 11 to the common crankshaft 300 for providing additional poweroutput. In other embodiments, additional engines 18 are coupled to thecommon crankshaft 300 in a parallel relationship, such as shown in FIG.24.

Multi-engines, such as those shown above, provide additional powerflexibility by providing a relatively simple means for decoupling one ormore of the engines from the crankshaft for incremental power reduction.

The above is a detailed description of particular embodiments of theinvention. It is recognized that departures from the disclosedembodiments may be within the scope of this invention and that obviousmodifications will occur to a person skilled in the art. It is theintent of the applicant that the invention include alternativeimplementations known in the art that perform the same functions asthose disclosed. This specification should not be construed to undulynarrow the full scope of protection to which the invention is entitled.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or acts for performing the functions incombination with other claimed elements as specifically claimed.

1. An internal combustion engine comprising: two opposed cylinders, eachcylinder having a cylinder liner adapted to accept two opposed pistonstherein defining a combustion chamber therebetween, the opposed pistonsadapted to reciprocate along a common axis, the cylinder liner furthercomprising intake ports and exhaust ports; a crankshaft disposed betweenthe cylinders, the crankshaft comprising journals; a housing adapted tohouse the cylinders; and a scavenge pump associated with each cylinder,the scavenge pump comprising a first scavenging chamber and a secondscavenging chamber, the first scavenging chamber defined by an end ofthe housing and a plunger linked to one of the opposed pistons distalfrom the crankshaft, wherein the plunger is adapted to move in unisonwith the piston and to draw in a fluid from outside the housing and toexpel fluid to the second scavenging chamber, the second scavengingchamber adapted to expel fluid into the combustion chamber through theintake ports.
 2. The engine of claim 1 wherein the second scavengingchamber of each of the two cylinders are in fluid communication.
 3. Theengine of claim 1 wherein the crankshaft has asymmetrically arrangedjournals, the engine further comprising: pushrods coupling one of thetwo opposed pistons proximate the crankshaft to at least one sharedjournal; and pullrods coupling one of the two opposed pistons distal thecrankshaft to at least one shared journal.
 4. The engine of claim 1wherein the second scavenging chamber of each of the two cylinders arenot in fluid communication.
 5. The engine of claim 1 wherein each pairof opposed pistons further comprises an outer piston distal from thecrankshaft and an inner piston proximate the crankshaft, the enginefurther comprising: at least one pushrod in urging engagement with eachof the inner pistons at a first end and coupled to at least one sharedjournal on the crankshaft at a second end, wherein at least one pushrodcomprises a second end comprising two tangs; and at least one pullrod inurging engagement with each of the outer pistons and coupled to at leastone shared journal on the crankshaft.
 6. An internal combustion enginecomprising: at least two opposed cylinders, each cylinder comprising onepair of opposed pistons reciprocating along a common axis, each pair ofopposing pistons defining a combustion chamber therebetween; acrankshaft comprising a first journal and a second journal, each pair ofopposed pistons further comprises an outer piston distal from thecrankshaft and an inner piston proximate the crankshaft; at least onepair of pushrods, each pushrod of one pair of pushrods coupled with oneof the inner pistons at a pushrod first end and coupled to the firstjournal on the crankshaft at a pushrod second end, wherein one of thepushrods comprises a pushrod second end comprising a single tang and theother pushrod comprises a pushrod second end comprising two tangsadapted to receive the single tang therebetween: and at least one pairof pullrods, each pullrod of one pair of pullrods coupled with one ofthe outer pistons at a pullrod first end and coupled to the secondjournal on the crankshaft at a pullrod second end, wherein one of thepullrods comprises a pullrod second end comprising a single tang and theother pullrod comprises a pullrod second end comprising two tangsadapted to receive the single tang therebetween.
 7. The engine of claim6 further comprising a second pair of pullrods, the crankshaft furthercomprising a third journal, the first journal positioned substantiallybetween the second journal and third journal, each pullrod of the secondpair of pullrods coupled with one of the outer pistons at a pullrodfirst end and coupled to the third journal at a pullrod second end, oneof the pullrods comprises a pullrod second end comprising a single tangand the other pullrod comprises a pullrod second end comprising twotangs adapted to receive the single tang therebetween.
 8. The engine ofclaim 6 wherein the at least two opposed cylinders are located on acommon axis.
 9. The engine of claim 6 further comprising: a bearingelement disposed between each of the two tangs and the single tang. 10.The engine of claim 6 further comprising: a scavenge pump associatedwith each cylinder, the scavenge pump comprising a first scavengingchamber and a second scavenging chamber, the first scavenging chamberdefined by an end of a housing and a plunger linked to the outer pistonwherein the plunger is adapted to move in unison with the piston and todraw in a fluid from outside the housing and to expel fluid to thesecond scavenging chamber, the second scavenging chamber adapted toexpel fluid into the combustion chamber.
 11. The engine of claim 9further comprising a lubrication port disposed in one of the single tangand the two tangs and associated conduit adapted to provide a lubricantto the bearing element.
 12. The engine of claim 6 wherein the crankshaftis a built-up crankshaft.
 13. An internal combustion engine comprising:two pairs of opposed pistons reciprocating along a common axis, and anend of each opposed piston, in conjunction with a cylinder, defining acombustion chamber; a crankshaft disposed between the two pairs ofopposed pistons, the crankshaft having a first journal; and a connectingelement linking each piston at an end of the piston opposite thecombustion chamber, wherein at least a pair of connecting elementscoupled to the first journal and movably aligned substantially along acommon axis.
 14. The engine of claim 13 further comprising at least twopairs of connecting elements, the crankshaft having a second journalwherein each pair of connecting elements is coupled to one of the firstand second journals and is aligned on an associated common axis.
 15. Anengine comprising: an internal combustion engine comprising two opposedcylinders, each cylinder comprising at least one pair of opposed pistonsreciprocating along a common axis, and an end of each opposed piston, inconjunction with a cylinder, defining a combustion chamber; a crankshaftconnected to at least one piston by at least one connecting element, thecrankshaft having at least one journal for coupling the connectingelement; and a scavenge pump associated with each cylinder, the scavengepump comprising a first scavenging chamber and a second scavengingchamber, the first scavenging chamber defined by an end of a housing anda plunger linked to one of the opposed pistons distal from thecrankshaft, wherein the plunger is adapted to move in unison with thepiston and to draw in a fluid from outside the housing and to expelfluid to the second scavenging chamber, the second scavenging chamberadapted to expel fluid into the combustion chamber.
 16. The engine ofclaim 15 wherein external radiating fins are disposed externally arounda portion of the cylinder for heat transfer.
 17. The engine of claim 16wherein the radiating fins comprise fins having a helical pattern. 18.An engine comprising: an internal combustion engine comprising at leasttwo opposed cylinders, each cylinder comprising at least one pair ofopposed pistons reciprocating along a common axis, and an end of eachopposed piston, in conjunction with a cylinder, defining a combustionchamber; and the pair of opposed pistons comprising an inner piston andan outer piston; the cylinder comprises at least one exhaust portdisposed so that reciprocation of the inner piston opens and closes theexhaust port, and at least one intake port disposed so thatreciprocation of the outer piston opens and closes the intake port; acrankshaft linked to the inner piston by a push rod, and the crankshaftlinked to the outer piston by an pull rod wherein rotation of thecrankshaft causes asymmetric port timing.
 19. The engine of claim 18further comprising: a scavenge pump associated with each cylinder, thescavenge pump comprising a first scavenging chamber and a secondscavenging chamber, the first scavenging chamber defined by an end of ahousing and a plunger linked to one of the opposed pistons distal fromthe crankshaft, wherein the plunger is adapted to move in unison withthe piston and to draw in a fluid from outside the housing and to expelfluid to the second scavenging chamber, the second scavenging chamberadapted to expel fluid into the combustion chamber.
 20. The engine ofclaim 19 wherein the crankshaft journals are arranged to present theopening of the intake port after the closing of the exhaust port. 21.The engine of claim 18 wherein the crankshaft is adapted so that thereis a phase angle of about 20 degrees between the intake ports and theexhaust ports.
 22. An engine comprising: a piston disposed in acylinder, one end of the piston cooperating with the cylinder to form acombustion chamber, the other end of the piston linked to a plunger, theplunger moves in unison with the piston; and a scavenge pump associatedwith the engine, the scavenge pump comprising a first scavenge chamberadapted to receive the plunger.
 23. The engine of claim 22 wherein thescavenge pump further comprises a second scavenge chamber in fluidcommunication with the first chamber; and a transfer valve disposedbetween the first fluid chamber and the second fluid chamber so thatfluid displaced by the plunger may be directed in one direction.
 24. Theengine of claim 22 wherein the scavenge pump further comprises: a fluidtransfer conduit having a transfer valve, the fluid transfer conduitbeing in fluid communication with the first scavenge chamber so that anexternal fluid may be introduced to the assembly.
 25. The engine ofclaim 22 wherein the cylinder further comprises at least one intake portin fluid communication with the scavenge pump so that reciprocatingmotion of the plunger directs an external fluid into the cylinder. 26.An internal combustion engine comprising: at least two opposedcylinders, each cylinder including at least one first piston, thepistons in the opposing cylinders reciprocating along a common axis, apiston and its respective cylinder, defining a combustion chamber; acrankshaft disposed between the cylinders comprising at least onejournal, wherein the first pistons are each coupled to respective endsof inner-piston pushrods, and the opposite ends of the inner-pistonpushrods are coupled to a common first journal on the crankshaft. 27.The engine of claim 26 wherein a crank-shaft coupling-end of one pushrod complementarily receives the crank-shaft coupling-end of the otherpushrod.
 28. The engine of claim 26 further comprising a second pistonin each cylinder to form a pair of opposed pistons in a cylinder, ineach pair the second pistons being the outer pistons from thecrankshaft, each pair movable on a common axis and defining a combustionchamber, and wherein the second pistons are each coupled to respectiveends of outer-piston pullrods, and the opposite ends of the outer-pistonpullrods are coupled to a common second journal on the crankshaft. 29.The engine of claim 28 wherein a crank-shaft coupling-end of one pullrod complementarily receives the crank-shaft coupling-end of the otherpullrod.
 30. A set of pullrods or pushrods adapted to couple to a commonjournal, according to claim 29.